In order to provide reusable or disposable receptacles for the storage of, for example, food stuffs or beverages, it is commonly known to employ the established process of blow moulding. The process, involving the use of compressed air, is utilized to deform or blow both low and high density plastics (LDP and HDP), polyethene (PET) and even glass into disposable milk bottles, food stuff containers, drink containers etc.
With reference to FIG. 1, the process of blow moulding utilizes a compressed air source 100 being connected to a compressed air manifold 101, being operable to transport the compressed air to the point of use 102 within a mould 103. In the case where a plastic material is deformed or blown at the point of use, the molten plastic is first dripped onto a needle 104 from where the compressed air emerges. Air is forced into the molten plastic which expands up to the extremity within the mould, thereby forming the receptacle.
The compressed air within the manifold 101 and mould 102 is then exhausted prior to the opening of mould 103 to remove the formed receptacle, ready for a repeat cycle. It is known in the art to control the blow moulding process using a suitable programmable logic circuit (PLC) thereby negating the need for human intervention and increasing the efficiency of the process with regard to compressed air consumption and blow moulding cycle time.
Further, multiple points of use being positioned on a central manifold, have been found to provide a more efficient blow moulding process as detailed with reference to FIG. 2. Compressed air is supplied into the manifold 101 from the compressed air source 100 into each mould 103 at each point of use 102. It is known to utilize valves 200 to control the transporting and providing of compressed air to the points of use. A feature common to all prior art blow moulding apparatus is the utilization and positioning of an exhaust valve 201 within the blow moulding apparatus. A typical prior art blow moulding device comprises an exhaust 201 being connected directly to the manifold 101 via a suitable valve 202. Such that, following the deforming of the material at the points of use 102 to form the receptacles, compressed air from within each mould 103 and the entire manifold 101 is exhausted at exhaust 201 via the opening of valve 202. Moulds 103 can then be opened to remove the formed receptacles and the blow moulding cycle repeated.
The inventors through familiarization with the blow moulding apparatus and method, have realized various problems and disadvantages with the employment of an exhaust valve connected directly to the manifold. The identified problems include:                As a result of compressed air within the moulds and the manifold being exhausted, compressed air consumption for any given blow moulding cycle is excessive due to the exhausting of compressed air from within the manifold. Moreover, the problem is exaggerated if the manifold is constructed from relatively large internal diameter tubing, as is found in the art.        The cycle time of any single blow moulding cycle is extended due to the requirement for the exhausting of compressed air from within the manifold. The volume of compressed air within the manifold is considerable and requires additional time for exhausting with respect to the volume of compressed air within each mould.        
The inventors have realized a need for a blow moulding apparatus and method that utilizes a plurality of exhaust points being positioned at each point of use (in close proximity to the mould), such that a blow moulding device is configured to exhaust compressed air from within the mould cavity only without resort to the unnecessary exhausting of large volumes of compressed air within the manifold. As such, compressed air consumption for any given blow moulding cycle may be reduced in addition to a reduction in the cycle time as a result of the capability to exhaust at the points of use, whereby a comparatively small volume of compressed air is exhausted. An improved blow moulding device is described herein below.